The extraction kinetics of anthocyanins and proanthocyanidins from grape to wine in three different varieties

摘要

Aims: To study the influence of the grape variety (Syrah, Monastrell and Cabernet Sauvignon) on the extraction kinetics of phenolic compounds (proanthocyanidins (PAs) and anthocyanins) during a skin maceration period of 20 days.Methods and results: Anthocyanins and PAs were analyzed by HPLC in three wine varieties during maceration time (20 days). The results showed that anthocyanin extraction followed the same kinetics for the three varieties. In the case of PAs, Syrah must-wine showed the highest concentration of these compounds, which were seen to be mainly skin-derived. Monastrell must-wine presented the lowest concentration of total PAs and the lowest percentage of skin-derived PAs. Cabernet Sauvignon must-wine obtained intermediate values for total PAs, although these compounds were more polymerized.Conclusion: Grape variety and extractability play a very important role in the wine PA profile. Thus, the highest values of total PAs were observed in the wines of Cabernet Sauvignon and especially Syrah.Significant and impact of the study: Knowledge of the kinetics of each variety during the maceration step may help manage the composition of wines in light of consumer preference. IntroductionPhenolics, mainly anthocyanins and proanthocyanidins (PAs), are important compounds in red wine quality because they influence colour, mouthfeel and aging ability. Studies have shown that overall intensity and persistence are positively correlated with astringency, and therefore to PA content (Mercurio et al., 2010). An optimal extraction of phenolic compounds from the skin and seeds of grape berries is crucial to ensure colour stabilization in the resulting wines and to impart desirable mouthfeel properties. The diffusion of the different polyphenols from grape to must-wine and, consequently, their extractability and final concentration at the end of the maceration process largely depends on their location in the berry and the characteristics of the different grape varieties, especially those related to the concentration in phenolic compounds and the extractability of these polyphenols.Anthocyanins are located in the skins, in the upper cellular layers of the hypodermis, while PAs are found in both skins and seeds. Skin PAs are mainly located in the skin cell vacuoles (Amrani-Joutei et al., 1994), while seed PAs are found in the epidermis, the outer integument and the inner integument (Cadot et al., 2006). PAs with upper dihydroxylated unit are called procyanidins and are present in grape skin and seeds, and PAs with upper trihydroxylated unit are called prodelphinidins and are present only in grape skin (Prieur et al., 1994; Souquet et al., 1996). Grape skin PAs have a higher mean degree of polymerization (mDP) and a lower proportion of galloylated subunits than seed PAs.Both the quantity and the extractability of anthocyanins and tannins increase throughout the grape ripening. The tannins and anthocyanins form different complexes with the cell wall components during berry development (Geny et al., 2003). As the berry ripens these complexes are broken up more easily than in unripe berries. During the maceration step of the winemaking process, phenolic compounds are extracted from grapes into wine. Anthocyanins are mainly extracted in the first days of fermentative maceration (González-Neves et al., 2008), and most skin PAs, due to their localization, are also solubilized, together with anthocyanins. However, the extraction of seed PAs takes longer. Seed PAs are diffused more slowly and require longer maceration times, while their extraction is favoured by the presence of ethanol (Canals et al., 2005; González-Manzano et al., 2004; Del Llaudy et al., 2008). This different extraction dynamics of PAs from grape into wine is therefore an important aspect to be considered when managing the maceration time (Singleton and Draper, 1964; Boulton, 1995), although it may also be influenced by the grape variety and the technological process applied at the winery, e.g., the extent of berry crushing, pectinolytic enzyme addition, the use of dry ice or the application of low prefermentative temperature (Canals et al., 2008; Cerpa-Calderón and Kennedy, 2008; Busse-Valverde et al., 2011; Hernández-Jiménez et al., 2012; Bautista-Ortín et al., 2013).Grape variety is one of the factors that have an important influence on the phenolic (PAs and anthocyanins) concentration and composition of the wine. Gonzalez-Neves et al. (2008) studied the influence of grape variety on the extraction of anthocyanins during fermentation on skins in three varieties (Cabernet Sauvignon, Merlot and Tannat) and concluded that the anthocyanin fingerprint of the young wines obtained in classical fermentation is characteristic of each variety, although their initial evolution follows general tendencies. In the case of PAs, Busse-Valverde et al. (2010) reported differences in the PA composition of Monastrell, Syrah and Cabernet Sauvignon wines that were more re